"When you visit Google Maps with a supported web browser, you'll see a new My Location button in the top left corner of the map," said Google Product Manager Steve Block on the company's blog. "Simply click the button to center the map to your approximate location. If your location can be determined accurately enough, it's shown with a blue circle, just like on Google Maps for Mobile. Click the button again to remove the blue circle, or to re-center the map after you've moved it away."
How Google does this has much to do with the reference to 'supported browsers'. Maps take advantage of the W3C Geolocation API standard which enables any website to access your current location. This feature was recently brought to an Internet Explorer toolbar but can now be integrated directly into any browser that supports the new Geolocation API which currently means Google Chrome 2.0+, Mozilla FireFox 3.5+ or any with Google Gears installed.

With no cell towers to triangulate (unless you're using a 3G dongle) the Geolocation API uses mapped WiFi access points and even golden oldie your computer's IP address. Accuracy can vary but in city centres it tends to be extremely precise.

So it's a simple addition but the potential is huge. As smartphone users will attest few things are more convenient than planning a journey by entering your destination and simply attributing the starting positing as your current location. So if you travel a lot with a laptop expect life to now get that bit easier...